I remember when I first started in this great hobby of ours, I was at loss for sites to go hunting.  Of course, I started in June, and shortly thereafter, the weather got hot and dry.  I am providing this listing of sites so that new and experienced MD'ers can find places to go search.

General Tips
 

• Sand and woodchip playgrounds are a great place for the newbie to start.  Get a good sand scoop or sand sifter for the sandpits.  In woodchip playgrounds, you can usually find the coin by using your foot to scrape away the top layer of chips.  I also use a small plastic hand rake to get through the "hard-pan" packed layer.  Coins don't usually get too deep in those, unless the City or Park employees add more woodchips.
• When you're in a playground, look around.  The "obvious" hotspots are anywhere a kid (or adult) can hang upside down.  All sorts of things fall out of pockets then.
• Also, look around swingsets.  I have found some coins directly under the swing (be sure to move the swing, as it will give you a signal itself), but mostly, you will find that the coins are generally found from the support "legs" of the swingset to about 10 feet or so out.  I figure that when the kids jump out of a swing, that's when they loose their coins.
• Teeter-totters are good; look around the seat at the ends.  You'll want to lift the seat up so it doesn't mask any targets.
• Slides are nice, where they land.
• Take the time to look around and observe.  Look where the kids are playing, and how they are playing.  If they are wrestling around on the ground, make a note of that location and come back when they are gone.  You might also want to search any other likely looking areas.
• Underneath bleachers are really, REALLY, trashy.  Plus, the metal posts will interfer with your detector.  Use a small coil, and preferable a machine that isn't very sensitive.  I might just build a small sifter and hit a few of these areas....
• If you go to a Junior High or High School, you might want to take the time to observe where the kids hang out at.  This is where you will most likely find coins and/or jewelry.
• Sports Fields!  I've had good luck at a couple "retired" football fields.  As a general rule, sports fields are fairly clean.  I put on my 10.5" coil and hunt in All-metal mode.  This gives me better depth and area coverage.  Be careful as to which sports field you hunt, and whether or not that field is in use at the time.  If a team shows up to practice, I'll leave, since I don't like getting tackled and/or beaned upside the head with a ball.  Also, "prime" fields, like the main High School football/baseball field, will most likely take permission from the groundskeeper.  These fields are carefully manicured to maintain the best appearance/footing.  Going out and digging monster holes and messing the place up is a sure way to get booted out.  But, practice fields, City Sports parks, etc., are good.  
• If the ground is dry as a bone and rock hard, try to find some over-grown, grassy areas.  The ground will not be rock hard there, but you may have to mow it first.
• Ask around in your town if there is an area where people go to throw away a wedding band from a failed engagement/marriage.  These sites are replenished at a good rate.
• Public Beaches!  In OK, the only public beaches are on the many area lakes.  These take a bit of looking.  Usually, in the water is OK, since that's Corps. of Engineer property.  But, land hunting is iffy, so ask at the gate.  If it's a State Park, that's a different jurisdiction, and may have different rules.  If you're lucky enough to own a boat, go scouting, looking for small, out-of-the-way beaches that are only accessible by water.  When I was in MI, there are county parks with beaches, and there are State Parks with beaches.  County parks are fair game.  State Parks, are only huntable in those areas "improved for recreational use".
• Anytime you see a sidewalk being torn up, hit that dirt!  But, be careful.  The city I lived in up in MI used coal-clinkers to level the bed for a sidewalk.  Those are negative hot rocks, and will drive just about any detector (except a PI unit) completely nuts.
• County Fairgrounds, especially older ones, that where on dirt/grass, and have not been paved over.
• Church revival areas.  You'll probably need permission, as these will be held on Church property.
• Old swimming holes.  I've searched one, and had impressive results.
• Old lakeside resorts.  There are lots of them all over in Michigan.  Look around, and you might find some yourself.
• Picnic Groves
• Camps of different sorts, like Railroad construction, Lumber, Military, etc.
  

• Develop a "Research Folder".  I created a folder for my researching materials.  Any materials that I find that can be cut/pasted into a document are saved there, as well as lists and other information I find useful.  I've actually created documents which list the locations of ghost towns, railroad depots, rural post offices, etc., as well as providing an ariel picture of the site so that I'll know what to expect.
• Create a folder to bookmark useful websites in your web browser.  I probably have a couple hundred different websites bookmarked.  I keep them organized by type.  Be sure to back them up, and keep the backup file (and all your research) somewhere off your computer's HDD.  Computers do crash, and you don't want to loose your data.
• Go "scouting".  Look for older areas.  Try to find older homes, schools, churches, etc.
• Go to your local library and check out the History Section.  See if they have anything on what your area was like 100 or more years ago.  Look for old maps, newspaper archieves, etc.   Plat maps are great for this, as they're drawn to scale.  Not only can you find ghost towns and such, but you can also see where houses once where, as well as businesses (more likely to have moneychanging hands and falling to the ground).
• Find out if your town has a Historical Society.  Become good friends with them.  If any of your research from their materials leads to a nice site, you might even want to donate some of your finds, and/or create a display for them.
• Talk to the Senior citizens in your area.  They know where everything took place back when they were children.  Such as, country fairs, local swimming holes, etc.  Besides, they'd probably love someone to talk to.
• Try to get some older topographical maps of your area.  These maps will show older schools, churches, country stores, towns, roads, trails, etc., that are no longer on the maps of today.
• Find out where the ghost towns in your area are.
• Find out where any stage coach lines, trolley stations, "Interurban" trains, train stations, or older bus routes were, and where the stops were.  If you're lucky, you'll find a Transit token.  Sometimes tokens are worth more than money.
• Find out where the older trails or overland roads for wagon trains, armies, etc. are.  Try to find the campsites.  Usually, they are near water, especially a ford, and were also easily defendable, such as on high ground.